As a technique for improving output power of an engine, a method is known in which a turbocharger compresses intake air and feeds the compressed intake air to the engine (turbocharging), and this method is widely used for automotive engines and the like. A turbocharger normally includes a rotating shaft, a compressor provided on a first end side of the rotating shaft, and a turbine provided on a second end side of the rotating shaft. The turbocharger is configured to rotate the rotating shaft via a turbine using exhaust energy of exhaust gas, allowing a compressor to compress intake air.
In the turbocharger, the rotating shaft rotates at a very high speed, and thus, in general, a full-floating floating bearing in which the bearing itself rotates is provided on a turbine side and on a compressor side as described in Patent Document 1. In this floating bearing, a clearance between an inner diameter side of the floating bearing and the rotating shaft and a clearance between an outer diameter side of the floating bearing and a bearing housing are each filled with lubricant. The floating bearing can freely rotate between the rotating shaft and a center housing. An oil film is formed in the clearance between the rotating shaft and the floating bearing, and thus, the rotating shaft rotates while floating from the floating bearing.
The lubricant with which the clearances are filled is fed via an oil feeding passage formed in the center housing. The oil feeding passage includes an oil feeding passage through which the lubricant is fed toward the compressor-side floating bearing and an oil feeding passage through which the lubricant is fed toward the turbine-side floating bearing.
The lubricant fed via the oil feeding passages cools the rotating shaft via the compressor-side floating bearing and the turbine-side floating bearing. The lubricant having cooled the rotating shaft is discharged toward an oil drain outlet of the center housing.